This invention relates to data communication. In particular, the invention relates to reducing delay in communication networks.
A communication network is a collection of nodes to which communicating stations (e.g., computers, terminals) are attached. A node is essentially a switching device that moves the data from node to node until they reach the destination. There are two basic types of switching techniques: circuit switching and packet switching. Among the packet switching networks, frame relay has become popular recently.
Frame relay provides a packet-switching data communications capability that is used across the interface between user devices (e.g., routers, bridges, host machines) and network equipment (e.g., switching nodes). The network providing the frame relay interface (FRI) can be either a carrier-provided public network or a network of privately owned equipment serving a single enterprise.
As an interface between user and network equipment, frame relay provides a means for statistically multiplexing many logical data conversations (referred to as virtual circuits, or VC""s) over a single physical transmission link. Frame relay""s statistical multiplexing provides more flexible and efficient use of available bandwidth that time-division-multiplexing (TDM) techniques. Frame relay can be used without TDM techniques or on top of channels provided by TDM systems.
Voice Over Frame Relay (VoFR) as defined in the standard from the Frame Relay Forum (FRF) FRF.11, allows PBX""s to be similarly connected using frame relay permanent virtual circuits (PVC""s), replacing leased lines and lowering costs. In a multi-hop frame relay network using FRF.11 voice over frame relay, non-voice packets carried by the network are fragmented according to the FRF.12 specification. Non-voice packets may include real-time sensitive common channel signaling (CCS) packets used to setup and teardown voice calls that are being carried by the FRF.11 frame relay voice network (over a dedicated FRF.11 sub-channel) between two PBXs.
The problem with the current fragmentation and defragmentation schemes is delays in the processing of packets for transmission, especially when the fragmentation sizes between two data links are not the same. In a multi-hop network, each time a CCS packet arrives at a forwarding node, it is defragmented before it can be forwarded to the next hop. When the defragmented packet is forwarded, the FRF.11 frame relay link that it is forwarded into will require that the packet is fragmented again. In the general case, the fragmentation size on the two links may not be the same. The defragmentation followed by refragmentation process causes the packet to be delayed. This delay will accumulate for each FRF.11 hop added and may end up exceeding the timeout values for the PBXs communicating via the CCS protocol.
A method and apparatus are described to reduce delay in a communication network. A fragmentation unit re-assembles a packet received from a first data link. A refragmentation pipeline is coupled to the fragmentation unit to pipeline the re-assembled data for transmission to a second data link.
Other features and advantages of the invention will be apparent from the detailed description and drawings provided herein.